Mixed soap-complex grease compositions



United States Patent vllle, N. J., assignors to Esso Research andEngineering Company, a corporation of Delaware No Drawing. ApplicationFebruary 20, 1953,

Serial N0. 338,148

6 Claims. (Cl. 252-39) This invention relates to lubricating greasecompositions, and particularly to lubricating grease compositions havingoutstanding high temperature and structure stability properties. Moreparticularly the invention relates to a mixed soap grease containingcombined therein a minor amount of a low molecular weight salt in theform of a complex with the mixed soap.

The preparation of calcium base grease is old in the art and is welldescribed in the patent literature. Such greases are excellent instructure, water resistance, and appearance. However, the hightemperature properties of calcium greases are very poor. This is due tothe necessity of maintaining a certain amount of water in the greaseitself. At temperatures above about 200 F. the water of formulation isdriven off and the grease structure breaks down, resulting in separationof the oil.

It has recently been found, and is described in detail in copendingapplication, Serial Number 301,194, filed July 28, 1952, now Patent No.2,708,659, of which this application is a continuation-in-part, that acalcium base grease having all the advantages of water resistance andcharacteristic structural stability of the calcium greases, and having,in addition, excellent high temperature properties may be prepared bycombining with the calcium soap of the prior art varying amounts of asoap of a metal selected from the group consisting of magnesium, barium,and strontium. Certain processing steps are necessary for thepreparation of the greases described in the copending application whichare described in detail therein.

It has now been found, and forms the object of this invention, thatthese mixed base greases may be improved in structure stability and hightemperature performance by complexing with the mixed base soap, ametallic salt of a low molecular weight acid, preferably one having fromone to six carbon atoms. The incorporation of a salt of a low molecularweight acid in the complex form with the high molecular weight acid soapgives better high temperature performance and increased structurestability.

The mixed soap base The mixed soap base which serves as the thickeningagent for the improved grease compositions of this invention comprises amixture of the calcium soap of high molecular weight fatty acids and asoap of a metal selected from the class consisting of barium, strontium,

and magnesium.

The high molecular weight fatty acids operable in preparing the mixedsoaps may be selected from the well atoms.

The calcium soap must be present in amounts ranging from about 2.5% toabout 15.0% by weight, based on the weightof the finished formulation.The amount of the soap of the second metal used is such. that the molratio of the c'alcium soap to the second soap is within the range offrom 8:1 to 1:8, with a mol ratio within the range of from 8:1 to 3:1being especially preferred. The amount of the'combined soaps presentwill depend somewhat upon thedesired'final consistency ofthe'product.Ordinary usage would call for a grease composition according to theinstant invention containing from about 5.0% to 30.0% by weight of thecombined soap, with a range of from 10.0% to 20.0% being especiallypreferred.

The complexing salt The low molecular weight organic acid salt which isused to form the complex with the mixture of high molecular'weight acidsoaps can be derived from any number of organic acids having from one tosix carbon The use of acetic or propionic acid is desirable, with aceticbeing preferred and used in the preferred embodiment. The metal used maybe selected from the class consisting of calcium, barium, magnesium, orstrontium, with the former being preferred. The salt may be added to thesoap mixture in the form of a slurry of the dry salt and oil, in the.form of the dry salt, or it may be prepared in situ. The amount of thesalt used will be such as to result in a mol ratio of the total soap tosalt of about 0.70 to about 1.2. M01 ratios of greater than 1.2 or lessthan 0.7 will not produce the results desired. A mol ratio of mixedsoaps to the salt of from 0.75 to 1.0 is especially preferred.

The lubricating oil base The lubricating oil which is utilized as adispersant for the soaps in'preparing the greases of invention may beselected from a wide variety of lubricating oils. A mineral lubricatingoil preferably of naphthenic origin may be chosen as the base. It shouldhave a viscosity within a range of from about 40 SUS at F. to about 4000SUS at 100 F. As in the preparation of most grease compositions, themineral oil chosen should be that lubricating oil which would be used tofurnish proper lubrication if a liquid oil could be used. preferred touse a mineral oil having a viscosity of from about 200 to 1500 SUS at100 F. to'formulate the greases of the preferred embodiment.

Although a mineral lubricating oil, such as a conventionally refineddistillate, is preferred for the preparation of the improved greases ofinvention, a synthetic oil may also be utilized as the dispersing agent.Although a synthetic lubricant of the ester type is preferred, such asthe esters of dibasic acids and long chain alcohols, other well knownsynthetic lubricants may be used. Complex esters made from dibasicacids, glycols, and alcohols, may be used, as may the polymerized glycolesters, glycol ethers, polymerized olefins, alkylated aromatics,polymerized silicones, formals, rnercaptals, and the like. The onlyrequisite for the oil base is that the one chosen be one that willfurnish the desired lubrication when utilized as a grease.

Method .of preparation The same two process limitations described indetail in copending application, ,Serial Number 301,194, pertain to themanufacture of the instant grease formulations; namely, the dispersionof the calcium soap prior to the dispersion of the second soap andheating the total formulation to a temperature of at least 350911 after.dehydration. The exact reasons are not known whythese limitations arecritical, but again it is believed that the solu- 3 tion of the calciumsoap in the oil aids in the dispersion of the second soap and that above350 F. there is a phase transition of the soap mixture which produces anew arrangement of molecules that is stable both at low and elevatedtemperatures. It is also-essential to-raise the mixture to these hightemperatures in order to form the complex of the mixture of soaps andthe salt, a complex which is believed to be largely responsible for theexcellent high temperature and shear stability properties 4 hightemperature properties could be improved. This is illustrated by thedata of Examples 2 and 3. The data on Examples 4 through 9, prepared inaccordance with the instant invention show both excellent hightemperature properties and excellent structural stability, at varioussoap concentrations and complex proportions. It seems clear that thecombination ofan alkaline earth metal salt of low molecular weight acidswith a mixture of two alkaline earth metal soaps of high molecularweight fatty obtained. to acids produces a grease that is superior toeither one The method of manufacture of the greases of this informedfrom a mere combination of low 'molecular vention may be generallydescribed'as follows. weight salts and a single high molecular weightsoap, or p The mixture of high molecular weight soap is prepared amixture of two high molecular weight oaps alone. first by saponifying apart of the saponifiable material Calcium acetate seems to be the mostefiective comwith calcium hydroxide in the presence of one third ofplexing agent, with barium acetate being very acceptable. the-totalamount of base oil. Then barium hydroxide is Other additive materials,such as oxidation inhibitors, added in the form of a slurry or as a drypowder to sacolor agents, stringiness or tackiness agents and the likeponify the remainder of the fatty acid. Calcium acetate may also be usedin preparing the greases of invention. barium acetate, as the Case y isthen added 88 a These agents are ordinarily added after the heating hasdry powder or as a water or oil suspension, or if desired been completedand before the grease has cooled coniit may be formed in situ. The soapsare dehydrated and m r ly, heated to above about 350 F. The remainder ofthe To reiterate briefly, the instant invention relates to base Oil iSthen added and the mixture heated to 450 F. superior high temperaturelubricating grease composito 480 F. At that temperature the mixture is ahomogetions that are prepared by complexing with a mixture neoussemi-solid mass. While stirring continuously the of the metallic saltsof high molecular weight fatty grease is cooled until the temperature isin the neighboracids, a metallic salt of a low molecular weight acid. df 50 The Stirring is Then pp and the Specifically, the alkaline earthmetals are desired, such grease cooled to room temperature. It is thenthoroughly as calcium, barium, strontium, and magnesium. Parworked, asby passing through a Morehouse mill or other ticularly desired andcontemplated in the preferred emwell known working device. bodiment arethe mixtures of the calcium and barium To illustrate the concept of thisinvention and to point soaps of high molecularv weight fatty acidscomplexed out the advantages of the new grease formulations over withthe calcium salt of a low molecular weight acid those of the prior art,nine grease samples were prepared. having from one to six carbon atoms.Mol ratios of The first preparation was carried out in accordance withfrom 8:1 to 1:8 of calcium soap to barium soap is the literature and acomplex of calcium soap and a calcontemplated, with the 'total soapmixture comprising cium salt was prepared. The second and thirdformulafrom about 5.0 wt. percent to 30.0 wt. percent of the tions wereprepared as described in Serial Number total formulation. The lowmolecular weight salt is 301,194, the copending application mentionedabove. added in amounts such that there is present a mol ratio Examples4 through 9 were prepared in accordance with of total soap to salt offrom 0.70 to 1.2, preferably the inventive concept as described indetail above. These from 0.75 to 1.0. It is also essential that thecalcium grease samples were submitted to the standard grease in soap bedispersed prior to the dispersion of the barium spection tests includingthe penetration tests, the detersoap in the mineral oil. mination of theneutralization numbers and the resistance What is claimed is: to boilingwater. The data obtained on these 9 greases 1. A lubricating greasecomposition having outstandare set out in table form below. ing hightemperature properties which comprises a lubri- TABLE Example No 1 2 3 45 v 6 7 8 9 High Mo] Wt. Soap Type Ca (la/Ba Cir Ba (Jo/Ba C's/Ba (Ia/BaC's/Ba Ca/Ba Oa/Ba High Mol Wt. Soap, M01 Rat-10.. 1 8/ 4/1 8/1 4/1 4/14/1 4/1 3/1 Percent Saponlf.Material 17 10 10 10 12.5 12.5 10 10 Low M01Wt. Salt Type Oa-Acc- Ca-Ace- C0-A.ce- Cu-Ace- Ca-Ace- Ba-Ace- Ba-Acetatate tats tate tats tats tate Percent Low M01 Wt. Salt 3 3 3 2 3 3 M01tib lz iiiol wt Salt l m l 1.07 1.07 1.07 0.86 0. 57 0.66 0. 86 DroppingPoint, 9 F 452 308 282 +520 +520 +520 340 414 3st Penetration inmIIL/IOI Unworkcd' 320 219 286 20s 258 175 175 375 318 Worked (10,000

Worker) 1 430 272 325 368 320 243 280 322 345 Neut. Number, PercentNaOEL 0.12 0. 73 0.13 0. 22 0.28 0. 30 0. 32 0. 47 0. 25 Resistance toboiling water fair excel. excel. excel. excel. excel. excel. excel.excel.

Typical Composition of a Sample (In weight percent):

10% Hydrogenated Fish Oil Acids 3% Calcium acetate 1. 23% Ba(OH)28HzO1.24% Ca(OH)1 84.48% D10] 2 l Using plate with small holes.

1 Acid treated coastal distillate having a viscosity of 70 S. U. S. at210 F.

The data of the table above point out the advantage of the greasesprepared in accordance with the inventive concept. It will be noted thatthe calcium-calcium acetate complex grease of the prior art, Example 1,has excellent high temperature properties, but that it fiuidizes after10,000 strokes with the fine hole worker indicating a lack of structuralstability. The Ca/Ba grease of Serial No. 301,194 has excellentstructural stability but its group consisting of calcium, barium,magnesium and strontium, the calcium soap being present in an amountranging from about 2.5 to 15.0% by weight, based on the weight of thetotal composition, the moi ratio of said calcium soap to said secondsoap being about 8:1 to 1:8, the mol ratio of said mixture of soaps tosaid metal salt being within the range of about 0.70 to 1.2, saidcomplex being formed by first dispersing the calcium soap in thelubricating oil, then dispersing the second soap and said metal salt,and heating the resulting mixture to a transition temperature from about350 to 480 F. 1

2. A lubricating grease composition according to claim 1 wherein thelubricating oil is thickened with from about 10.0 to 20.0% by weight ofthe complex, based on the weight of the total composition, the mol ratioof said calcium soap to said second soap is between about 8:1 to 3:1,and the mol ratio of said mixture of soaps to said metal is betweenabout 0.75 to 1.0.

3. A lubricating grease composition according to claim 1 wherein saidfatty acid contains about 12 to 24 carbon atoms.

- 1 wherein said second soap is a barium soap.

5. A lubricating grease composition according to claim 1 wherein saidfatty acid is hydrogenated fish oil acid.

6. A lubricating grease composition according to claim 1 wherein saidsalt is calcium acetate.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,032 Zimmer et al. Ian. 25, 1949 2,070,781 Brunstrum et'al Feb. 16,1937 2,197,263 Carmichael et al. Apr. 16,1940 2,389,523 Leyda Nov. 20,1945 2,417,429 McLennan Mar. 18, 1947 2,417,433 McLennan Mar. 18, 19472,495,651 Butcosk Ian. 24, 1950 2,513,680 Shott et al. July 4, 19502,553,423 Shepard May 15, 1951 2,564,561 Carmichael et a1 Aug. 14, 19512,583,394 Shott et al. Jan. 22, 1952

1. A LUBRICATING GREASE COMPOSITION HAVING OUTSTANDING HIGH TEMPERATUREPROPERTIES WHICH COMPRISES A LUBRICATING OIL THICKNESS WITH FROM ABOUT5.0 TO 30.0% BY WEIGHT, BASED ON THE WEIGHT OF THE TOTAL COMPOSITION, OFA COMPLEX FORMED FROM A MIXTURE OF A CALCIUM SOAP AND A SECOND SOAPSELECTED FROM THE GROUP CONSISTING OF BARIUM, STRONTIUM AND MAGNESIUMSOAPS OF HIGH MOLECULAR WEIGHT FATTY ACIDS AND A METAL SALT OF A LOWMOLECULAR WEIGHT CARBOXYLIC ACID HAVING FROM ONE TO SIX CARBON ATOMS,SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF CALCIUM, BARIUM,MAGNESIUM AND STRONTIUM, THE CALCIUM SOAP BEING PRESENT IN AN AMOUNTRANGING FROM ABOUT 2.5 TO 15.0% BY WEIGHT, BASED ON THE WEIGHT OF THETOTAL COMPOSITION, THE MOL RATIO OF SAID CALCIUM SOAP TO SAID SECONDSOAP BEING ABOUT .8:1 TO 1:8, THE MOL RATIO OF SAID MIXTURE OF SOAPS TOSAID METAL SALT BEING WITHIN THE RANGE OF ABOUT 0.70 TO 1.2, SAIDCOMPLEX BEING FORMED BY FIRST DISPERSING THE CALCIUM SOAP IN THELUBRICATING OIL, THEN DISPERSING THE SECOND SOAP AND SAID METAL SALT,AND HEATING THE RESULTING MIXTURE TO A TRANSITION TEMPERATURE FROM ABOUT350* TO 480* F.